Lightning on Venus Strikingly Similar to Earth's

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Lightning on
Venus and Earth may spark in much the same way despite vast differences in the
atmospheres of the two planets, scientists say.

" Venus and Earth are often called twin planets
because of their similar size, mass and interior structure," said Christopher
Russell, lead author of the new lightning study and a professor at the
University of California, Los Angeles." The generation of lightning is one
more way in which Venus and Earth are fraternal twins."

Russell and
his colleagues used new data from Venus Express to show that lightning is
similar in strength on Earth and Venus at the same altitudes on both worlds.

"We
have analyzed 3.5 Earth-years of Venus lightning data using the low-altitude
Venus Express data (10 minutes per day)," Russell said. "By comparing
the electromagnetic waves produced at the two planets, we found stronger
magnetic signals on Venus, but when converted to energy flux we found very
similar lightning strength."

The data
also show that lightning is more prevalent on the planet's dayside than at
night, and occurs more often at low latitudes, where the solar input to the
atmosphere is strongest.

These
results will help scientists better understand the chemistry, dynamics and
evolution of the atmospheres of the two neighboring planets. Russell will present the findings tomorrow (Sept. 23) at the European Planetary Science
Congress in Rome.

Previous
missions to Venus, including the Soviet Venera spacecraft, NASA's Pioneer Venus
orbiter and the robotic Galileo spacecraft, have detected optical and
electromagnetic waves from the cloud-covered planet that could be produced by
lightning. [ Photos:
Lightning on Earth ]

Ground-based
telescopes have also captured evidence of lightning flashes on Venus, but from a theoretical standpoint,
the topic has been controversial.

Since the
atmospheres of Venus and Earth are so different, some scientists have claimed
that Venusian lightning is unlikely if it exists at all. The clouds of Venus are much like smog clouds on Earth, which
typically do not generate lightning.

The European
Space Agency's Venus Express probe currently orbiting the planet has since shed
some light on how the two worlds are, in fact, more similar than previously
thought.

Tracking
Venus lightning

To track
Venusian lightning , the Venus Express probe is equipped with a magnetometer that
monitors the planet's magnetic field at altitudes between 124-310 miles
(200-500 kilometers).

The
instrument has picked up low-frequency radio waves that last for a split second
and are thought to come from electrical discharges.

"Short,
strong pulses of the signals expected to be produced by lightning were seen
almost immediately upon arrival at Venus, despite the generally unfavorable
magnetic-field orientation for entry of the signals into the Venus ionosphere
at the altitude of the Venus Express measurements," Russell explained.

When clouds
form, on Earth or Venus, the energy that the sun has deposited into the air can
be released in the form of a very powerful electrical discharge.

As cloud
particles collide in the atmosphere, electrical charges are transferred from
the larger ones to the small. The large particles fall, while the small
particles are carried upward. This separation of charges leads to lightning strikes.

Science
of lightning bolts

Studying how
lightning is generated in a planet's atmosphere is important because the phenomenon
can raise the temperature and pressure of a small portion of a world's overall
atmosphere to a very high degree, enabling molecules to form. This would
otherwise not occur at standard atmospheric temperatures and pressures.